Blood and judgment

The woman's partially buried body is found near the reservoir. She’s been murdered. What is soon called the reservoir case is assigned to Detective Sergeant Petrella of the London police force (who is constantly having to explain to people that he isn't as young as he looks.) Petrella's first job is to identify the woman. She turns out to be the wife of a criminal who's escaped from prison. Has her fugitive husband killed her? And if he has, why? The case becomes more complicated. Clues point in many directions and even back in time. Then another body is discovered.